A Phoenix man is accused of murdering his pregnant girlfriend last week, as police say his story unraveled because he failed to properly light the crime scene on fire.

Dwandarrius Robinson, 21, faces murder, arson, and kidnapping charges after the body of his girlfriend, Shaniqua Hall, was found bound in burning inside the couple's apartment.

According to court documents obtained by New Times, Robinson called 9-1-1 on July 12, reporting a fire at his apartment and saying he was "unsure" whether Hall was inside.

A firefighter found Hall's body on fire, between the wall and the bed in the master bedroom.

Hall's hands and feet were bound, with a strip of duct tape covering her eyes, according to the documents.

Robinson was in the apartment complex's courtyard during this time, holding his and Hall's 2-year-old girl.

Robinson told police he was at work all morning, and when he got off work at 1 p.m., he went to a grocery store -- to buy lighter fluid and duct tape, the documents state.

Police say Robinson had an explanation: the duct tape was for a "box project," and the lighter fluid was for a barbeque they were having a few days later -- the day Hall was due to deliver her new baby.

Robinson told the cops he then went to a friend's place to pay off a $5 marijuana debt, then took his daughter to Burger King for lunch.

When he came back to the apartment shortly before 2 p.m., he said he heard the fire alarm going off, and saw that the windows were black with smoke, and he could smell the smoke as he approached.

The first problem with that, police note, is that the first officer to enter the apartment didn't see any black smoke in the windows, nor did he smell any smoke until he actually went inside.

Robinson told the cops he called 9-1-1, then sat in his car to run the air conditioning "since he was hot."

He said he never went inside the apartment -- even though he thought his girlfriend and unborn child were inside -- because "he feared being burned and leaving his children orphaned," the documents state.

Aside from the duct tape connection, police say Hall's hands were bound behind her back with handcuffs.